In a conventional power supply system, a power source outputs a high frequency alternating current power to a power line and multiple communication devices wirelessly receive the high frequency alternating current power from the power line (for example, refer to Patent Literature 1).
Further, a communication system includes parallel power supply lines through which communication signals propagate and a pickup device that receives the communication signals from the parallel power supply lines via a coupling device (for example, refer to Patent Literature 2).
Based on the systems disclosed in above-described Patent Literature 1 and Patent Literature 2, the inventors of the present disclosure studied on a communication system having a power line and a communication device. In this communication system, the power line transfers a superposition of high frequency power and a communication signal, and the communication device receives the high frequency power and the communication signal via a coupling device in a electromagnetic induction manner. After the study on this communication system, the inventors of the present disclosure found that a part of the high frequency alternating current power and the communication signals leak as electromagnetic waves at a portion other than the coupling device.